1. Field of the Invention
The present invention relates generally to hinges for folding ladders, and more particularly, to a safety unit of a hinge for a folding ladder, which prevents a user's finger from being undesirably caught in the hinge when the hinge rotates.
2. Description of the Related Art
Generally, a ladder comprises a rod- or tube-shaped frame which is made of metal. Since the ladder is large in volume, the ladder is manufactured to be foldable. FIGS. 1 and 2 show conventional hinges for folding ladders. As shown in FIG. 1, the hinge 10 includes a first joint unit 12 having a pair of discs, a second joint unit 14 having one disc, a locking unit 18, and a guide disc (not shown). The first and second joint units 12 and 14 are coupled to each other by a central shaft 16, and pivot on the central shaft 16 while rotating relative to each other. The guide disc is provided between the discs of the first joint unit 12 to be operated in cooperation with the second joint unit 14. Thus, according to a position of the guide disc, the locking unit 18 provided at a predetermined portion of the first joint unit 12 engage with one of notches 20 provided along a peripheral edge of the disc of the second joint unit 14, so that the first and second joint units 12 and 14 are locked at a desired angular position.
However, when a strong impact acts on the hinge 10 in a state where the hinge 10 is angled at 180°, the hinge 10 may be undesirably folded or a load may be concentrated on the central shaft 16, thus causing deformation of the central shaft 16 and thereby leading to a malfunction of the hinge 10.
In order to solve this problem, as shown in FIG. 2, the first and second joint units 12 and 14 have first and second stop shoulders 22 and 24, respectively, thus preventing the hinge 10 from further rotating when the first and second joint units 12 and 14 are angled at 180°.
However, such a hinge 10 has a problem in that a user's finger may be caught between the first and second stop shoulders 22 and 24, when the second joint unit 14 rotates relative to the first joint unit 12 and the first and second stop shoulders 22 and 24 come into contact with each other.